Process and composition for electrical etching.



J. H. WEEKS.

PROCESS AND COMPOSlTlON run ELECTRICAL ETCHING. APPLICATION FILED JULY8.1916.

1 289,022. Patented Dec. 24, 1918.

4 SHEETS-SHEET l.

J. H. WEEKS. PROCESS ANDCOMPOSITION FOB ELECTRICAL ET CHING.

APPLICATION FILED JULY 6.191s.

1,289,022. Patented Dec.24,1918.

-4 SHEETS-SHEET 2.

I. H WEEKS.

PROCESS AND COMPOSITION FOR ELECTRICAL ETCHING. APPLICATION FILED JULY8,1916.

1,289,022; Patented Dec. 24, 1918.

4 SHEETS-SHEET 3.

(1110: new

J. H WEEKS. PROCESS AND COMPOSITION FOR ELECTRICAL ETCHING.

APPLICATION FILED JULY 8.1916.

1 ,289,022. Patented Dec. 24, 1918.

4 SHEETS-SHEET 4- A UNITED STATES PATENT orr on.

JOSEPH HENRY WEEKS, or RUTLEDGE, PENNSYLVANIA, AssIGNOR T0 JACKSON s.

WEEKS, OF DELAWARE .COUNTY, PENNSYLVANIA, AND- BAYMOND M. WEEKS, 0F

PHILADELPHIA, PENNSYLVANIA, TRUSTEES.

PROCESS AND COMPOSITION FOR ELECTRICAL ETCHING.

To all whom it may concern:

Be it known that I, JOSEPH H. WEEKS, a citizen of the United States,residing at Rutledge, in the county of Delaware and State ofPennsylvania, have invented certain new and useful Improvements inProcesses and Compositions for Electrical Etching, of which thefollowing is a specification, reference being had therein to theaccompanying drawing.

y and has for its object the provision of an 1mproved process of andcomposition for electrical etching as hereinafter described.

The present invention is a continuation in part of my prior application,88,362, filed April 1, 1916, and is an improvement thereon in certainparticulars,

l in the accompanying the sides and ends of especially in regard to thecomposition of the electrolyte.

Certain forms'of apparatus made use of in carrying out my invention areillustrated drawings to which reference will be had in the descriptionand in which- Figu proved etching tank used in carrying invention.

Fig. 2 is a continuation of Fig. 1 showing in perspective the drivingmechanism.

Fig. 3 is a perspective view partly in section of the etching tankequipped with mechanically driven brushes for removing sludge from thecathodes.

out my Fig. 4: is a detail of theadjustable brush holder. v Fig. 5 is aperspective detail view showing the arrangement of the brush in thisholder. Fig. 6 is a detail of the brush rod adjustment. Z

Fig. 7 is a detail of the link connection between the brush mechanismand the operating shaft.

Fig. 8 is a plan view of a'tank witha plate suspended therein, facedown, and cathodes hung vertically upon wires along the tank.

Fig. 9 is a longitudinal view of the same partly in section, showingcams and slides for raising and lowering the plate in the solution whileetching.

Referring to the drawings,

Specification of Letters Patent.

. material.

invention relates to electrical etching Serial No.

re 1 is a. perspective view of the imand especially Patented Dec. 24,1918.

Application filed July 8, 1916. Serial No. 108,232.

to Figs. 1 and .2, 1 indicates an etching tank which may be of anysuitable waterproof and insulating material, or other kind of materialrendered waterproof on the inside, such as wood coated on the insidewith an insulating waterproof and chemical resisting The usual draincock 2 is provided for the purpose of draining the tank when necessaryto chan e the solution or empty for repairs. Positioned within the tankaround the four sides thereof so as to be immersed and substantiallysurround the electrolyte, are the cathodes 3 which may be of anysuitable conducting material but are preferably of carbon. As it isdiflicult to obtain and use, with economy, carbon plates of thedimensions and proportions desired, I find it expedient and advantageousto form these cathodes of a number of'carbon plates 4: held andprotected by a frame 5. Electrical connection is made between thecathode plates 4 and a bus 6 by means of a plurality of flexibleconducting members 7 extending in parallel connection between the saidcathode plates and bus bar. This bus bar 6 extends entirely around theoutside of the etching tank near the top thereof, so as to afford theshortest possible connection between it and the cathode plates. Normallyresting upon the top of the tank and extending longitudinally thereof,is a continuous plate support 8 which rests upon the opposite ends'ofthe tank 1 and is prevented from comin in contact with the flexibleconnections 'of the end cathode plates by the insulating blocks 9. Eachof these blocks 9 is provided with transverse channels 10 in its lowersurface to accommodate the conductors 7 and carries on its upper surfacea pair of vertical guide rods 11 positioned near the ends of the blocksso as to include the plate support 8 and prevent lateral displacementthereof during its up anddown movement.

In this up and down movement of the plate support 8 it is desirable thatit be given a certain cycle of operation which I have found makes forbetter results and therefore constitutes an important part of theprocess to which the present invention pertains. The driving andoperating mechanism for producing the movement of the plate supportconsists of a suitable prime mover such as the electric motor 12 mountedabove the tank on the platform'13 supported on suitable wall bracketssuch as 1%. The motor'12 is connected through a reducing worm ear 15 toa countershaft 16 running parallefto the etching tanks, of which theremay be any number, and carrying at its ends a pair ofthis arrangementthe comparatively slow ro-' tary movement of the shaft 16 is transformedinto a variable vertical movement of the sliding shaft 19, due to thecrank and pitman connection between them, shaft 19 having a higher speedmidway of its extreme positions than at the extreme positions.

By adjusting the length of the flexible connections 21, 1 may obtainvarious degrees of lost motion between the plate support 8 and the shaft19, whereby the continuous motion of the shaft 19 may be transformedinto an intermittent motion of the plate support, the cycle of which maybe varied as regards the. relative periods of rest and movements byadjustment of the length of the flexible connections 21. For example ifthe flexible connections 21 are so adjusted that when the shaft 19 is atits highest point, the plate support 8 will swing a given distance abovethe insulating blocks 9, this distance will represent the limit of theamount of vertical movement given to the plate support 8 and through itto any plates suspended therefrom in the electrolyte, any furthermovement that would otherwise be transmitted to it from the rod 19 beinglost through. the flexible connection when the plate support comes torest on the insulating blocks 9. Thus any plates carried by the support8 will remain at rest in the solution during a certain portion of thecycle and be moved during" the remainder, the extent of movement and therelative duration of the rest and moving periods depending upon theamount of lost motion between the shaft 19 and support 8, while theduration of the complete cycle would be determined by the speed at whichthe driving apparatus is operated. It is not desirable to have theplates move all the time, although this may be accomplished by adjustingthe flexible connections 21 in a manner that will be obvious. In anycase the plates. are of course immersed all the time. As a specificexample of an adjustment to produce a give cycle, if the full' stroke ofthe rod 19 is 11 inches and the connections 21 are adjusted to raise theplates only 2 inches, the time of motion of the plates will be 2/11 01the whole cycle, while the period of rest will be 9/11 of the wholecycle.

During etching an occasional interruptlon of the current is desirable,and in fact important, because it tends to keep the face of the anode(the plate being etched) clean, and assists in producing smoothness ofetching. A plateto be so treated is indicated at 22 which is suspendedfrom the support 8 by a suitable metalli hook 23 through which itreceives current from the conducting sup port and which hook is soarranged that it may be lifted out of connection with the member 8 tointerrupt the flow of current to the plate 22. This lifting of the hook23 with a resultin interruption of the current fiow is effectedperiodically by means of a suitable flexible connection 2 1 connectingthe hook with the sliding rod 19 and so adjusted as to its length thatthe lost motion between the hook 23 and the rod 19 will be taken upbefore that of the'support 8, thus causing the hook 23 to be raisedslightly in advance of the support 8 and held out of electrical contactwith the support until it again comes to rest on the insulating blocks9, when the connection 21 becomes slack and after that the connection24, permitting the hook 23 to again come to rest on the support 8 inelectrical contact therewith. Thus, in the case of a plate connected as22, it is not only periodically moved up and down in the electrolyte buthas its supply of curren periodically cut ofl', the duration of eitherof which conditions may be varied by suit able adjustment of theflexible connections 21 and 241 in a manner which will be obvious. it isfurther to be noted that, if desired, the plate 22 may be made to remainstationary during the whole cycle of movement of the running'parallel tothe several tanks and supported above and back of them on a suitableinsulating wall support 27. From these bus bars connection is madethrough suitable protected flexible cables 2829 and 30-31, to theconducting support 8 and bus 6, respectively. As a low voltage currentis usually employed in apparatus of this kind and an even distributionof the volume of the current, is essential, the arrangement of certainconnections must be such as to avoid any difference in the drop ofpotential at the different points of connection. It is to this end thatthe connection is made from opposite ends of the support 8 throughseparate conductors 28 and 29 to individual positive bus bar members 25,and from opposite ends to the bus members 25 and 26 will be subjected toa voltage slightly higher than the farther tanks but with thearrangement of connection shown, this will not affect the evendistribution of current as regards the individual tanks.

Where it is desired to surround the electrolyte on all four sides andbottom with the cathode members, a fifth cathode member is rovided,which substantially covers the ottom of the tank and to which connectionis made to all four edges thereof from the four sides of the bus 6 bymeans of conducting members such as 32 passing through the side walls ofthe tank through suitable watertight insulating bushings 33.

When electrolytes are employed which tend to form sludge or a coating onthe cathodes,- -I provide mechanical means for disengaging the sludgeand keeping the oathodes clean. A preferred form of this means is hereillustrated in Figs. 3 to 7 inclusive, and while for the sake ofclearness I have not shownit combined with the arrangement of Figs; 1and 2, it is to be understood, of course, that it is to be usedin-combination with the former arrangement of apparatus, that is inassociation with a common tank. This cleaning arrangement consistsgenerallyof a set of brushes 34 arranged to be moved up and down acrossthe inner faces of the cathodes by suitable reciprocating mechanism suchas the sliding shaft arrangement of Fig. 1 preferably identicaltherewith and which shall be so described.

Referring more in detail to the structure of the cleaning mechanism, thebrushes 34 are connected to the side 'rods of the rectangular frame 35through adjustable connecting devices 36 each comprising a frame or rodengaging portion 37 in the form of a collar and set screw and a brushengaging portion 38 in the form of a C clamp having a pointed anchorstud 39 and clamping screws 40. With this novel form of connectionbetween the brushes and the frame, the brushes may be set either tocause the edge or the entire. face to engage the cathode. To take upwear between the brushes and the cathodes, the rods. forming the frame35 are connected at each of the four sides through right and leftthreaded turn buckles 41. The brush carrying frame 35 is carried by apair of forked rods 42 the tines of each fork connecting with thecorners at opposite ends of the frame.. The arm 43 of each forked rodcarries a bifurcated member 44 1n which is pivotally secured the lowerend of a connecting rod 45 having a U shaped head 46,0pen at the sideand adapted to straddle the sliding shaft 19. The space between the armsof the U-shaped head is slightly ta ered toward the open end so thatwhen the ead is slid over the rod 19 the open end only will offer anappreciable resistanc, the closed end fitti'ng freely around the shaft.To secure connecting rod 46 "against disengagement from the shaft 19, a

bolt orpin 47 is provided which extends across the open side throughperforations 48 therein.

It will be seen that the forked members 42 are amply wide enough topermit free. operation of the plate support 8 andeasy access to thedifferent parts by the operator.

When this cathode cleaning mechanism is used, it is preferable to omitthe fifth or bottom cathode. Y

Figs. 8 and 9 show another form and arrangement of a tank andappurtenances for carrying out my process. In these figures, projections50 on the sides of the tank carry a wire or rod 51. extending around theentire upper part of the tank and having extension terminals connectedto the negative terminal of the source of current.

My cathodes 52, consisting preferably of carbon rods provided with metalcaps and hooks at their upper ends, are hung from this wire. In Fig. 9twelve of these cathodes are swung, but the number is immaterial, so

long as their combined surface is greater than the surface "of the anodeor plate to be etched. A liberal allowance in this respect is productiveof good results. The anode or plate is shown at 53, suspended face down'I from a pair of rods 54, consisting of copper wire bent in a loop ateach end, and connected at both ends to the positive terminal of thesource of current, which is preferably a (fynamo of low voltage, but maybe any convenient and suitable source.

When a large quantity of solutionis employed, the up and down motion ofthe anode can be dispensed with, but I consider it very desirable togently move the anode at constantly' recurring intervals as beforedescribed for Fig.1. Mechanism for producing this motion of the plate isalso provided in the form of apparatus shown in Figs. 8 and 9. I hereshow ashaft 55 beneath the tank, with its ends journaled in bearingssecured thereto, provided with a pulley 56 at one end for attachment toany suitable driv- 7 .ing means. Vertical slides 57 are provided 8 and9. This is geometrically shaped, preferably with triangular ends,sloping sides, and its longitudinal ridge lying directly under the anodeplate. It is made of acidresistant material or wood or metal coated withthe same and water-tight. This filler is shown at 61, in dotted lines,in Figs. 8 and 9.

I consider it novel and original with me to arrange the cathodes in themanner shown and described in the several figures so as to permit aneven distribution of the current in all part-s of the bath. I havehitherto Worked upon the generally accepted theory that the anode andcathode must face each other in parallelism so that the passage ofcurrent from one to the other through the bath should be in lines asnearly normal to both surfaces as possible; but experience has shown methat this is unnecessary, provided that the points of suificient surfaceand even distribution of current are taken care of.

For the solution or electrolyte in the tank, I may employ any one of anumber of formulas, all well known to those skilled in the art. Theregular electrotypers formula so-called,

consists of sulfate of copper dissolved in water to make a solutiontesting 10 on the Baum hydrometer, with sufficient sulfuric acid addedto bring the hydrometer test to 15. This may be used, but I prefercertain formulas of my own, which I shall now state and shallhereinafter claim as a part of my invention.

Solution No. 1: Dissolve calcium chlorid in water until the solutionregisters from 5 (with heavy Baum hydrometer) to a point of almostsaturation. This solution can be acids, a smaller quantity thereof is reuired;

and the stronger the calcium chlori solution the larger the amount of,acid which may be employed. These acids increase the conductivity of thesolution, which also varies with the strength of the chlorid solution.The acids also serve to keep the face of the anode clean and bright.

Solution No. 2: This is made according to the foregoing formula,following the same remarks, but substituting sodium chlorid (commonsalt) in place of calcium chlorid.

Solution N0. 3: This solution is made in aeaoae exactly the same way andaccording to the same directions as No. 1, but ammonium chlorid(salammoniac) is substituted for the calcium chlorid.

Solution No. 4: Dissolve sodium chlorid in water until the solutiontests 5 Baum to saturation and combine in proper proportions a solutionof ammonium chlorid of from 5 Baum to saturation, adding any of theabove named acids until the desired conductivity and eifect on the anodeare produced.

Solution No. 5: Ammonium chlorid in water to a strength testing from 5Baum (heavy hydrometer) to saturation, to which is added from 5 percent. to 100 per cent., of the volume of the former, a solution ofperchlorid of iron containing an excess of acid; or a solution ofneutral chlorid of iron used with the addition of an acid, as mentionedin No. 1.

of iron of equivalent strength, or the equiva-- lent in dry chlorid ofiron; with or without the addition of any of the acids mentioned in No.1.

Solution No. 7 Ammonium chlorid in water to a strength testing from 5Baum- (heavy hydrometer) to saturation, to which is added in anyproportion desired a solution of sodium chlorid in Water testing from 5Baum (heavy hydrometer) to saturation, and to the combined solutions isadded from 5 per cent. to 100 per cent. of the volume of the former,solution of perchlorid of iron of about 42 strength, or chlorid of ironof equivalent strength, or the equivalent in dry;

chlorid of iron; with or without the addition of any of the acidsmentioned in No. 1.

As illustrations of solutions produced by these formulas, I may note thefollowing:

No. 1. Calcium chlorid in water to Baum test 20 1 gal. Hydrochloric acidC. Pu; 14 oz. No. 2. Ammonium chlorid in water to Baum test 20 1 gal.Sulfuric acid 1- oz. No. 3. Sodium chlorid in water to Baum test 20 1gal.

Sulfuric aci n 1% oz. No. 4. .Sodium chlorid in water test 15 a gal.Ammonium chlorid in water test 15 2 gal. Hydrochloric acid 1 oz.

Under certain conditions I find it of further advantage to lastly add toeach of the solutions 5, 6 and 7. from 1} per cent. to 15 per cent., ofthe total preceding volume,

hydrochloric acid C. P., or the equivalent of hydrochloric acid oflesser strength. Other acids may also be employed as previouslyindicated.

Having thus described the apparatus'and composition of the electrolytes,I shall now proceed with the steps in the operation. The first stepconsistsin producing the image 'on the plate by any of the photographicor transfer methods well known in the graphic arts.

The back of the plate is next coated with an insulating material, whichmay be chosen from a great variety, such as shellac dissolved inalcohol, a solution of asphaltum and paraffin, or almost any wax likesubstance, to which has been added a resin or asphaltum, or both.

Theplate is then connected with the positive wire of a dynamo or batteryand immersed in a suitable electrolyte, constituting the anode terminaltherein. I have found it preferable and shall claim it as original, tomaintain the plate horizontally in the electrolyte with the face (theside contain ing the image) downward, as hereinbefore described.

In line plates or what is known as line portions of combination plates,after a certain depth is attained, which is technically termed (inchemical etching), the first bite or first etch, powdering with resinousor waxous powder is necessary. A variety of such powders have been inuse, for a long time, by photo-engravers and others employing acidchemical means, to prevent the thinning of the lines by side etching,which would soon be followed by under cutting, or under etching of thelines, and'if carried to an extreme degree, would necessarily take thelin away entirely,'or if only to a slight extent, would interfere withthe duplication of the plate by electro-typing or stereotyping. Toprevent this side etching and thinning of, the lines after havingobtained a certain depth, reinforcingthe side of the lines must be donein four directions, whether the plate be etched electrically orchemically, and this I must therefore do inmy electrical etching method,although I am able to obtain a greater depth before this becomesnecessary than is possible in chemical etching. It may readily be seenthat in very small spaces, such as between lines that are approximatelyone fiftieth of an inch apart, the powder entirely fills the opening andthis receives no further etching after the first etching, so that thedepth of the plate in such fine portions, therefore, depends entirelyupon the etching. Herein I claim great superiority owing to the factthat my plate is 50 per cent. to 100 percent. deeper than the old platesbefore the necessity for powdering arises.

After powdering more or less of a; shoulated. Shoulders, it may beadded, increase der is produced, hence by getting m plate so muc deeperin the first etching, t e possibility of shoulders on the sides of thelines n'earthe' printing surface is entirely obvithe difficulty ofprinting any plate.

It will be apparent to those skilled in the art that some sundry changesand modifications may be made in'the apparatus, in the method and insuch details as the formulas of the electrolyte, etc. Thus, I may employplates of various metals or substances, to be etched, and I may employdivers metals or other substances instead of carbon for the cathode, andin the apparatus mechanical equivalents subserving the same function.For example adjustable rods engaging the sliding shaft 19 throughelongated eyes or 'loops maybe substituted for-the adjustablesubsequently added acid, as a matter of convenience, because theperchlorid of iron of commerce which is'on sale in eastern cities of theUnited States like "Philadelphia, contains approximately the correctexcess of acid. In some particular instances, on very delicate work, Ihave used the neutral iron combined with the sodium and ammonium oreither of them, where theresisting image was not thought to havesuflicient strength to resist the stronger action of an acid solution,

but such solutions would have no permanency. It is to be noted that theiron can be omitted in etching for some of the metals,

not including brass and copper, and with them it is to take care of thecopper content that I use the iron especially. Thus, on other metals, achlorid with an acid andllll) without the iron can be used and in somecases will work better. For this reason, and because the perchloridwhich I employ contains an excess of acid, I desire to emphasize thefact that the acid is an important constituent for permanency in myelectrolyte and is present in the chlorid and may also be used withoutthe iron: I shall therefore claim the solution with an acid and it is tobe understood that such claim'is generic to those claims specifyingperchlorid. It is to be also understood that while I have pointed outthe usefulness of the iron in etching copper or an alloy containingcopper, I do not wish to confine myself to such'use, as the perchloridof iron is both convenient and efiicacious with other metals, and can beused for example with steel, although I have not hitherto found it anessential ingredient in etching steel.

- rid of iron and hydrochloric acid.

I scribed, composed of a solution of a chlorid of a member or aquasi-member of the alka- Having thus described my invention what Iclaim and desire to secure by Letters Patent is:

1. An electrolyte for electrolytic etching, containing a solution of achlorid, to which perchlorid of iron has been added.

2. An electrolyte for electrolytic etching composed of a solution ofsodium chlorid to which has been added perchlorid of iron or anequivalent as hereinbefore set forth.

3. An electrolyte for electrolytic etching composed of a solution ofsodium chlorid to which has been added a quantity of perchlo- 4. Anelectrolyte for the purposes de line groupytowhich has been added aquantity of perchlorid of iron and hydrochloric acid.

5. An electrolyte for electrolytic etching composed of a solution ofsodium chlorid to which has been added perchlorid of iron or anequivalent, together with a quantity of acid.

6.'A n electrolyte for electrolytic etching composed of a combinedsolution of ammonium chlorid and sodium chlorid to which has been addedperchlorid of iron or an equivalent.

. 7. An electrolyte for electrolytic etching nasaoaa which has beenadded a quantity of perchlorid of iron and an acid.

10. An electrolyte for the purposes described composed of a solution ofammonium chlorid in water, combined with a solution of sodium chlorid inwater, both testing approximately the same degree Baum, to which hasbeen added a quantity of perchlorid of iron and an acid.

11. An electrolyteior electrolytic etching composed of the chlorid of amember or quasi-member of the alkali group, in solution, to which hasbeen added perchlorid of 12. An electrolyte for electrolytic etchingconsisting of chlorid of sodium from 5 Baum to a point of saturation,witha small percentage of acid.

. lln testimony whereof I affix my signature.

JUSEPH HENRY WEEKS.

